Lead for radio systems



Jan. 21, 1930 H. J. WRAPE LEAD FOR RADIO SYSTEMS Filed Aug. 18. 1922Patented Jan. 21, 1930 UNITED STATES PATENT OFFICE HAROLD J'. WRAPE, 01:8'1. LOUIS, MISSOURI, ASSIGNOR, BY-MESNE ASSIGNMENTS, TO BENWOOD-LINZECOMPANY, OF ST. LOUIS, MISSOURI, A CORPORATION OF MISSOURI LEAD FORRADIO SYSTEMS This invention pertains to apparatus for use in wirelesstelegraphy and telephony.

In many installations of radio apparatus, condensers are required tofurnish the required electrical capacity for proper tuning operations,adjustment of wave lengths, and similar purposes. In many cases theactual value of the capacity required is extremely small, and values aslow as 1/100 to 1/1000 of 10 a microfarad being used. In such cases thedimensions of a condenser constructed for such small capacity becomesvery small. In fact, two parallel wires of several feet in length havebeen found to have between them sufiicient capacity for some purposes.

One of the objects of this invention, therefore, is to provide aconnecting lead for use with radio apparatus which shall haveincorporated therein a. condenser of small capacity.

It is often found inconvenient or expensive to erect the necessaryantenna required for receiving or transmitting radio signals. In manycasses it is found convenient to utilize in place of the antenna, anexisting network of conductors such as, for instance, the electric lightwiring of an ordinary house.

Some difficulty is encountered in connecting to the light wiring of anordinary house, on account of the fact that such wiring is alwaysconnected'to the service mains and the current from such mains must bekept out of the radio apparatus.

Another object of this invention therefore is to provide a connectinglead or leads ,through which the radio set may be con- .nected to thehouse wiring as an antenna without interfering with the use of suchwiring for its normal purpose.

Another object is to provide a convenient form of connecting leads whichmay be attached to the house wiring by merely plugging into anordinary-lamp socket.

Further objects will appear from the following description taken inconnection with the accompanying drawing in which,

Figure 1 is a diagram illustrating the general method of connecting tothe house wiring through leads embodying this invention.

Figure 2 is a view illustrating a pair of leads embodying this inventionand attached to a standard plug.

Figure 3 illustrates the construction of a lead embodying thisinvention.

Figure 4 is a sectional view showing the connections to the plug.

Figure 5 is a View illustrating another embodiment of this invention.

-Referring now to the drawing and more particularly to Figures 2, 3, and4, 1 designates a lead which is made up of a pair of wires, 2, asillustrated in Figure 3. Each of the wires, 2, may be provided with-itsown insulation, 3. The pair of wires, 2, together with their insulation,3, may then be covered by a protecting cover, 4:, of braid or othersuitable material. The pair may then be provided with an outer covering,5, which may take the form of a rubber tube. This forms what isordinarily called a two-conductor or twin-conductor cable.

In accordance with this invention, two leads each made up of a pair ofwires as just described for Figure 3 are connected to a standardattachment plug, 6, as illustrated in Figure 4:. In this figure eachlead comprises a pair of wires as illustrated in Figure 3, one of whichis connected to one of the terminals, 7, of the plug. The other wire ofeach pair is dead-ended and insulated at the upper end of the lead, 1,while at the other end of the lead this conductor is connected to aterminal, 8. There is thus no conductive connection between theterminals, 7 and 8, but the two wires to each lead lie. parallel to oneanother at a short distance apart and form together a condenser of smallcapacity. The actual capacity of this condenser can be adjusted withinthe practical limits by varying the length of the lead.

In using this device the connection is made as illustrated in Figure 1,in which 9, designates the house wiring. 10 designates one coil of aradio transformer, of which 11 isthe other coil. The coil 10 isconnected to the main 9 through a pair of leads, 1, each lead comprisinga pair of wires, 2. It will be noted that one of each pair of wires 2,is connected to the mains, 9, while the other conductor, 2, of each pairis connected to the coil, 10. It will be noted that there is thus noconductive connection between the mains 9, and the coil, 10, so thatpractically none of the service current from the house circuit will flowthrough the coil, 10. Only such current as can pass through thecondenser formed by the wires, 2, can flow and, since the voltage andfrequency on the mains, 9, are comparatively very low, only a negligiblecurrent will flow from the mains through the coil, 10.

The conditions that obtain with this connection are, however, veryfavorablef r use in radio work. It will be understood that in ordinaryhouse wiring one of the mains, 9, is grounded while the other is not. Itwill be evident, therefore, that by this connection one terminal of thecoil, 10, will be connected through a light condenser to a network ofwires adapted to provide an effective antenna.

It is true that the grounded and ungrounded mains are connected togetherthrough the secondary coil of the service transformer.

The inductance of such a coil is, however, so high that currents ofradio frequency will not flow therethrough, so that the presence of sucha coil will not affect the operation of the system for radio work. Itwill be evident, therefore, that by simply inserting the plug, 6, intoany lamp socket connected to the mains, 9, the radio set will beconnected both to an effective ground and to an effective antenna.

While in the large majority of cases one side of the house wiring isgrounded, there are some cases in which the house circuit is notgrounded. In such case the radio set may be connected to one side of thehouse circuit by means of a single lead, and to the ground through aseparate lead.

Figure 5 illustrates an embodiment of this invention in which a smallamount of inductance as well as capacity is incorporated in theconnecting lead. In this embodiment a single wire, 2, is provided withan insulated coating, 3. Surrounding the insulated coating, 3, is acoiled metallic strip, 12, forming a so-called armor or protectivecovering for the wire. This combination is furnished to the trade by thename of Armored cable. The armor, 12, may be covered with an insulatingcovering, 5; At the upward end of the lead the wire, 2, may be connectedto a plug or other suitable terminal, not shown. At the lower end of thelead the armor, 12, is electrically connected to a terminal, 8.

It will be noted that the wire, 2, and the metallic armor, 12, beingparallel and close together, but insulated from one another, form twocoatings of a condenser. At the same time the armor, 12, being coiledwill have the effect of an inductance in the circuit in which the leadis connected. The relative values of inductance or capacity may be 65varied by varying the thickness of the insulation, 3, or the pitch ofthe coil of the armor, 12, or both.

It will be evident from the foregoing that the invention accomplishesits objects. A device is provided whereby a radio set may be connectedto the ordinary house mains in such a way that said-mains will furnishboth the ground connection and the antenna connection for the set. Atthe sametime interference of the house circuit with the operation of theset is effectively prevented. The connecting leads also furnish therequired small value of capacity for ordinary radio sets, particularlyamateur sets of which a The connection is efgreat many are in use.fected 1n the ver simple and direct manner by simply plugging into alamp socket. By

the device illustrated in Figure 5, inductance as well as capacity canbe inserted in the circuit.

It is obvious that various changes may be made in the details ofconstruction without departing from the spirit of this invention; it istherefore to be understood that this invention is not to be limited tothe specific details shown and described.

Having thus described the invention, what is claimed is:

1. In a radio system, a double pole plug, and leads, each of whichcomprises parallel filar conductors arranged to form a condenser, oneconductor from each lead being connected at one end to a terminal of theplug, the other end of said conductor being insulated.

2. In a radio system, a double pole plug, and a pair of leads, each ofwhich comprises a pair of parallel filar conductors arranged to form acondenser, one conductor of each lead being connected to a terminal ofsaid plug, the other end of said conductor being insulated, and thefirst end of the other conduct-or of each lead being insulated and itslast end provided with a terminal.

In testimony whereof I affix my signature this 18th day of July, 1922.

HAROLD J. \VRAPE.

